feat(userspace): shell runs programs (ls, cat) via spawn w/ terminal+storage+args page; ext4 holes read as zeros; storage re-attach same buffer

scripts/make-disk-image.sh

@@ -30,6 +30,10 @@ copy permission-manager "permis.elf"
 copy session-server     "session.elf"
 copy terminal-server    "terminal.elf"
 copy shell              "shell.elf"
+copy cat                "cat.elf"
+copy ls                 "ls.elf"
+# Files that ship on the disk.
+cp -r disk/. "${ROOT}/"
 # Only the test image: its presence makes init run the self-test.
 if [ -n "${SMPTEST:-}" ]; then
     copy smptest   "smptest.elf"